8 TALKS AFIELD. 



of blue, of yellow, or even green. Occasion- 

 ally the housewife is arrested in her work 

 by the appearance of blood-colored spots on 

 cold potatoes or other articles of food, and 

 as likely as not she half accepts the old su- 

 perstition which supposed them to indicate 

 the anger of God ; she does not suspect that 

 the spots are aggregations of many minute 

 living plants which have come from the air. 

 Bacteria are nearly everywhere present, in 

 the air, in all stagnant or impure water, in 

 all fermenting and decaying substances, and 

 often in the human body. When moist sub- 

 stances in which they grow become dried 

 up, they wither and escape as dust into the 

 atmosphere to be revivified when again they 

 fall under favorable conditions. In the air 

 near the suburbs of Paris M. Miguel finds 

 an average of about eighty bacteria to every 

 square yard of air. Some of these, mag- 

 nified a thousand times, are 

 shown in Fig. 7. The floating 

 dust in the sunbeam is com- 

 posed of larger bodies than 

 these bacteria. It is made up 

 largely of fragments of lint, of 

 Fig- 7- spores of moidds, and of pol- 



len of flowers. It is clearly demonstrated 



